Diabetes is one of the most prevalent chronic disorders worldwide with significant personal and financial costs for patients and their families, as well as for society. Different types of diabetes exist with distinct etiologies and pathogeneses. For example, diabetes mellitus is a disorder of carbohydrate metabolism, characterized by hyperglycemia and glycosuria and resulting from inadequate production or utilization of insulin.
NIDDM, or otherwise referred to as Type II diabetes, is the form of diabetes mellitus which occurs predominantly in adults in whom adequate production of insulin is available for use, yet a defect exists in insulin-mediated utilization and metabolism of glucose in peripheral tissues. Overt NIDDM is characterized by three major metabolic abnormalities: resistance to insulin-mediated glucose disposal, impairment of nutrient-stimulated insulin secretion, and overproduction of glucose by the liver. It has been shown that for some people with diabetes a genetic predisposition results in a mutation in the gene(s) coding for insulin and/or the insulin receptor and/or insulin-mediated signal transduction factor(s), thereby resulting in ineffective insulin and/or insulin-mediated effects thus impairing the utilization or metabolism of glucose.
Reports indicate that insulin secretion is often enhanced early-on, presumably as compensation for the insulin resistance. People who actually develop NIDDM appear to do so because their B-cells eventually fail to maintain sufficient insulin secretion to compensate for the insulin resistance. Mechanisms responsible for the B-cell failure have not been identified, but may be related to the chronic demands placed on the B-cells by peripheral insulin resistance and/or to the effects of hyperglycemia to impair B-cell function. The B-cell failure could also occur as an independent, inherent defect in "pre-diabetic" individuals.
NIDDM often develops from certain at risk populations, one such population is individuals with polycystic ovary syndrome (PCOS). PCOS is the most common endocrine disorder in women of reproductive age. This syndrome is characterized by hyperandrogenism and disordered gonadotropin secretion producing oligo- or anovulation. Recent prevalence estimates suggest that 5-10% of women between 18-44 years of age (about 5 million women, according to the 1990 census) have the full-blown syndrome of hyperandrogenism, chronic anovulation, and polycystic ovaries. Despite more than 50 years since its original description, the etiology of the syndrome remains unclear. The biochemical profile, ovarian morphology, and clinical features are non-specific; hence, the diagnosis remains one of exclusion of disorders, such as androgen-secreting tumors, Cushing's Syndrome, and late-onset congenital adrenal hyperplasia.
PCOS is associated with profound insulin resistance resulting in substantial hyperinsulinemia. As a result of their insulin resistance, PCOS women are at increased risk to develop NIDDM. Hirsutism, acne, and alopecia, which are commonly found in PCOS women, are clinical manifestations of hyperandrogenism. Menstrual disturbances and infertility are the result of ovulatory dysfunction related to the disordered gonadotropin secretion. Androgen excess, probably by eventual conversion of androgens to estrogen, also plays an important role in disrupting gonadotropin release in PCOS.
There are two leading hypotheses for the association between PCOS and insulin resistance: 1) androgens produce insulin resistance or 2) hyperinsulinemia produces hyperandrogenism. In support of the first hypothesis, synthetic androgen administration can increase insulin levels in women. However, in PCOS women with acanthosis nigricans (which is a marker for insulin resistance), oophorectomy lowers testosterone levels but does not alter insulin resistance. Further, long-acting GnRH agonist treatment in PCOS women decreases plasma testosterone and androstenedione levels into the normal female range, but does not alter glucose tolerance, insulin levels, or insulin action. Thus, although certain synthetic androgens may have a modest effect on insulin sensitivity, natural androgens do not produce insulin resistance of the magnitude found in PCOS.
In contrast, there are several lines of evidence that support the alternative hypothesis that hyperinsulinemia produces hyperandrogenism. First, extreme insulin resistance of a variety of etiologies, ranging from insulin receptor mutations to autoimmune insulin resistance, is associated with ovarian hyperandrogenism. Second, insulin can directly stimulate ovarian androgen secretion in vitro and in vivo in PCOS women. Finally, decreasing insulin levels for 10 days with diazoxide results in a significant decrease in testosterone levels in PCOS women. Insulin does not alter gonadotropin release but rather appears to act directly on the ovary. However, these actions of insulin are not observed in normal ovulatory women, suggesting that polycystic ovarian changes are necessary for such insulin effects to be manifested.
Insulin resistance in PCOS is secondary to a marked decrease in insulin receptor-mediated signal transduction and a modest, but significant, decrease in adipocyte GLUT4 content. In many PCOS women, the decrease in insulin receptor signaling is the result of intrinsic abnormalities in insulin receptor phosphorylation. The magnitude of insulin resistance in PCOS is similar to that in NIDDM and in obesity. However, the cellular mechanisms of insulin resistance appear to differ in PCOS compared to these other common insulin-resistant states. The shift to the right in the insulin dose-response curve for adipocyte glucose uptake is much more striking in PCOS than in obesity. Further, decreases in adipocyte insulin sensitivity and responsiveness are significantly correlated with hyperinsulinemia, glycemia, and/or obesity in individuals with NIDDM or obesity, whereas insulin resistance is independent of these parameters in PCOS. Finally, no persistent abnormalities in insulin receptor autophosphorylation have been identified in NIDDM or obesity.
NIDDM also develops from the at risk population of individuals with gestational diabetes mellitus (GDM). Pregnancy normally is associated with progressive resistance to insulin-mediated glucose disposal. In fact, insulin sensitivity is lower during late pregnancy than in nearly all other physiological conditions. The insulin resistance is thought to be mediated in large part by the effects of circulating hormones such as placental lactogen, progesterone, and cortisol, all of which are elevated during pregnancy. In the face of the insulin resistance, pancreatic B-cell responsiveness to glucose normally increases nearly 3-fold by late pregnancy, a response that serves to minimize the effect of insulin resistance on circulating glucose levels. Thus, pregnancy provides a major "stress-test" of the capacity for B-cells to compensate for insulin resistance.
Studies of insulin action and B-cell function during pregnancy indicate that, during the third trimester, women with mild-moderate GDM have the same degree of insulin resistance as do non-diabetic pregnant women. However, studies during the second trimester and after pregnancy indicate that women with GDM are somewhat insulin resistant compared to women who maintain normal glucose tolerance during pregnancy. Taken together, the available data indicate that pancreatic B-cells of women who develop GDM may encounter two types of insulin resistance: 1) mild-moderate, underlying, and perhaps genetic insulin resistance that is present even when the women are not pregnant; and 2) the marked, physiological (probably hormonally-mediated) insulin resistance that occurs during pregnancy in all women. Data indicate that the main feature which distinguishes women with GDM from normal pregnant women during the third trimester, when all women are insulin resistant, is pancreatic B-cell function. Most women develop GDM because their pancreatic B-cells are unable to maintain enhanced insulin secretion in the face of insulin resistance. That inability is very similar to the B-cell defect which has been observed in longitudinal studies of patients who develop NIDDM, a fact which may explain why women with GDM are at such high risk for NIDDM: GDM identifies women whose B-cells will decompensate when faced with severe or chronic insulin resistance.
Other populations thought to be at risk for developing NIDDM are persons with Syndrome X; persons with concomitant hyperinsulinemia; persons with insulin resistance characterized by hyperinsulinemia and by failure to respond to exogenous insulin; and persons with abnormal insulin and/or evidence of glucose disorders associated with excess circulating glucocorticoids, growth hormone, catecholamines, glucagon, parathyroid hormone, and other insulin-resistant conditions.
Failure to treat NIDDM can result in mortality due to cardiovascular disease and in other diabetic complications including retinopathy, nephropathy, and peripheral neuropathy. For many years treatment of NIDDM has involved a program aimed at lowering blood sugar with a combination of diet and exercise. Alternatively, treatment of NIDDM involved oral hypoglycemic agents, such as sulfonylureas alone or in combination with insulin injections. Recently, alphaglucosidase inhibitors, such as a carboys, have been shown to be effective in reducing the postprandial rise in blood glucose (Lefevre, et al., Drugs 1992;44: 29-38). In Europe and Canada another treatment used primarily in obese diabetics is metformin, a biguanide.
In any event, what is required is a method of treating at risk populations such as those with PCOS and GDM in order to prevent or delay the onset of NIDDM thereby bringing relief of symptoms, improving the quality of life, preventing acute and long-term complications, reducing mortality and treating accompanying disorders of the populations at risk for NIDDM. The methods of using the disclosed compounds for treating at risk populations with conditions such as PCOS and GDM to prevent or delay the onset of NIDDM as taught herein meet these objectives.
The compounds of the present invention, and methods of making the compounds, are known and some of these are disclosed in U.S. Pat. Nos. 5,223,522 issued Jun. 29, 1993; 5,132,317 issued Jul. 12, 1992; 5,120,754 issued Jun. 9, 1992; 5,061,717 issued Oct. 29, 1991; 4,897,405 issued Jan. 30, 1990; 4,873,255 issued Oct. 10, 1989; 4,687,777 issued Aug. 18, 1987; 4,572,912 issued Feb. 25, 1986; 4,287,200 issued Sep. 1, 1981. The compounds disclosed in these issued patents are useful as therapeutic agents for the treatment of diabetes, hyperglycemia, hypercholesterolemia, and hyperlipidemia. The teachings of these issued patents are incorporated herein by reference.
Regarding prevention of NIDDM, there has been one disclosure of this concept using a sulfonylurea as a treatment, but this concept is not highly regarded in the scientific community because prolonged treatment with sulfonylureas can reduce insulin secretion by destroying the pancreatic beta cells. Moreover, sulfonylureas can cause clinically severe hypoglycemia. The concept of using a biguanide, such as metformin, has also been disclosed.
There is no disclosure in the above-identified references to suggest the use of the compounds identified in this present application in the treatment of at risk populations such as those with PCOS or GDM in order to prevent or delay the onset of NIDDM and complications resulting therefrom.